There have recently been proposals to allow access to the features and services provided by cellular networks, such as GSM and UMTS networks, other than by accessing those networks in the conventional manner. In this regard, the conventional manner is by signalling between a mobile terminal and a conventional base station (macro base station) that has a dedicated connection to a Mobile Switching Centre (MSC). The MSC is a component of the network which controls radio resource management, in order to ensure that a user is connected to the best base station in terms of signal strength or quality.
It has been proposed to increase network capacity by providing additional special base stations, referred to here as micro base stations or access points (APs), for example at a subscriber's home or office. Many different names have been given to micro base stations such as access points (APs), home access points (HAPs), pico-base stations, pico-cells and femto-cells, but all names refer to the same apparatus. APs provide short range, localized cellular telecommunications coverage, and are typically purchased by, or rented to, a subscriber to be installed in their house or business premises.
These micro base stations may be dedicated network access points, or may be enhanced wireless internet hubs (i.e. providing wireless internet access, as well as wireless telecommunications network access). The range of micro base stations is significantly smaller than macro base stations, typically providing coverage to a range less than 100 metres.
Such APs can be installed and provisioned by the end consumer and may have a “closed” list of users who are able to connect to the access point. Where such an AP is installed at residential premises, these users could include the residents of the house, close friends and family as well as regular visitors who are known to the property owner.
By having a “closed” AP, only those users known to the consumer will be allowed to connect to the AP and so the resource is reliably reserved for those users. This contrasts with an “open” AP in which any user who is within the radio coverage of the AP can connect.
An advantage of introducing APs in existing telecommunications networks is that, where sufficient numbers of APs are implemented, the power level of the macro coverage could be reduced, due to a lower demand for the macro-base stations. Power reductions of course result in energy and financial savings, for instance due to less spectrum being required and also less hardware.
A further advantage of using an access point connected to the core network via an IP network is that existing broadband Digital Subscriber Line (DSL) connections can be used to link mobile terminals with the network core without using the capacity of the radio access network or transmission network of a mobile telecommunications network. In other words, the AP is be integrated into a DSL modem/router and uses DSL to backhaul the traffic to the communication network. This provides a high bandwidth and advantageously allows the AP to be capable of delivering services that require high data rates.
A still further advantage is that APs enable mobile network access to be provided in areas where there is no macro radio access network coverage. For example, an AP could provide 3G coverage in an area where there is no macro 3G coverage at all, perhaps only macro GSM coverage. The use of APs as an additional or alternative means for accessing the network, which therefore advantageously increases the network capacity.
However, additional challenges arise in implementing these access points in a well-integrated telecommunications network. For instance, because APs are. installed by a consumer they may be located in an area in which the radio coverage provided by the access point interferes with that of the existing cellular network. This occurs because both the AP and the cellular network are sharing the same frequency resource. In such cases, this interference can lead to localised coverage holes appearing in the existing cellular network. This arises because users not registered with the AP may experience a strong signal from it but are unable to connect to it because it is “closed”. This can lead to dropped calls in the cellular network, or forced handover to another radio system. Overall, the result is a degraded quality of service for many users in the cellular network and a reduction in the efficiency of the network as fewer users can be carried satisfactorily.
A further problem is that APs continually draw power to transmit a radio broadcast channel, as per the normal operation of a base station. In this regard, the broadcast channel is required to enable a user to initially “hear” whether it is in range of an AP and to support the required call set up signalling. However, for closed APs, since only a limited set of users can access it, the usage of it is likely to be intermittent or only for a short of time during the day. Therefore, being continuously operational and accordingly continuously consuming power, introduces a cost to the owner of the AP, and also has an adverse environmental impact due to the power wastage.
One solution to this problem is to let the end-user determine the “on-time” of the AP by powering it down when not in use, by physically switching it off at the mains switch. The user must then switch it back on when again requiring use of the AP. In practice, however may users will forget to switch off the AP, as it may be inconvenient to do so and as a result the owner will tally a greater bill for consumed electricity. In addition, the unnecessary transmission of broadcast channels by the AP will lead to increased interference in the surrounding network.
Further, if the user forgets to switch the AP back on, he may find himself connected unexpectedly to another base station and may experience a lower quality of service and/or a different tariff (e.g. where a reduced tariff is offered by the network provider when the AP is used as a base station).
Not only is powering down an AP by switching it off at the mains an ungraceful approach, but it may also result in data residing in the AP (e.g. network configuration information such as neighbouring cells and handover settings) being lost. This data would then need to be restored on power up, which would typically introduce delays into the power up procedure.